A wind consortium says it has successfully deployed a power curve measurement procedure that analyzes power output in constantly changing conditions.

The procedure is part of a consortium comprising DTU Wind Energy, DONG Energy, Siemens Wind Power and Avent Lidar Technology. The Danish Energy Technology Development and Demonstration Program provided funding for the three-year effort.

According to Avent, which recently mounted its WindIris LIDAR system atop a Siemens turbine at the 367 MW Walney Wind Farm, the procedure is an upgrade to using met masts, the traditional method to measure power performance.

"Measurements of wind turbine power curves are a key issue for the wind industry," explains Thomas Velociter, CEO at Avent. "But conducting power performance verifications with met-masts is often difficult and extremely expensive, particularly offshore or in onshore complex terrains, which means that verifications and measurements are sometimes skipped all together.

He says that nacelle-mounted LIDARs allow for accurate and affordable measurements, resulting in reduced cost of energy and increased competitiveness.

The technology has been submitted to the expert and standardization groups Measnet and IEA Task 32 in order to be upgraded to an internationally recognized standard. It opens new possibilities for cheaper and more frequent power performance measurements.

According to Avent, the project evolved from a ground-based WINDCUBE LIDAR from Leosphere, which was adapted to be placed on the turbine nacelle for forward looking horizontal measurements. Over the course of the project, several prototypes were developed and tested, and have evolved into a new product called WindIris, which integrates all the elements of the procedure.

The WindIris, manufactured and commercialized by Avent, has been specifically designed for turbine-mounted measurements, which require a product sturdy enough to endure adverse factors, such as nacelle vibrations.

"One of the main challenges was to obtain an equivalent procedure to the IEC 61400-12-1 power performance measurement standard," says Velociter. "To achieve the required level of accuracy and repeatability, the developed procedure accounts for each one of the measurement requirements. For example, it specifies how to measure at hub-height +/- 2.5% at 2.5 rotor diameter in front of the turbine and account for the deviation inherent to the flexibility of the turbine."